You may already know that chronic sleep deprivation is  linked to a host of health problems. But here's the kicker: Research suggests that oversleeping could actually be just as bad.

How much sleep do I really need?

The  National Sleep Foundation recommends seven to nine hours per night for people ages 18 to 64, and seven to eight hours for those ages 65 and older.

Sleeping less than that for even one night can leave you tired, grouchy, less productive and more accident-prone the next day. If you routinely sleep either too much or too little, your risk for type 2 diabetes, heart disease and stroke may be higher than if you had slept the recommended amount.

Too much of a good thing: How much is too much sleep?

Until recently, researchers paid considerably more attention to sleep exhaustion and sleep deprivation than to oversleeping. However, that's starting to change.

In one  eye-opening paper on shuteye, researchers analyzed data from 137 studies including more than 5.1 million people. Prolonged sleep was associated with an increased risk of developing diabetes, heart disease, stroke and obesity. It was even linked to an increased risk of dying early.

Another  interesting study looked at some of the physiological changes that may connect oversleeping to poor health. It showed that  sleeping either more than ten hours or less than six was associated with metabolic syndrome and its components. Metabolic syndrome is a cluster of risk factors that raise the risk of heart disease, stroke and diabetes. People with the condition must have at least three of the following:

• High blood sugar
• High triglycerides (a type of fat in the blood)
• Low HDL (“good") cholesterol
• Large waistline
• High blood pressure

Both men and women who slept longer than 10 hours were more likely to have higher triglycerides and metabolic syndrome, compared to those who slept a healthy amount. Women who slept that long were also more likely to have higher blood sugar, lower HDL, and larger waistlines.

Connecting zzz's to disease

There are several ways in which sleeping too much could potentially be linked to risk factors and disease. According to  researchers at Uppsala University in Sweden, an overly long snooze time may:

• Be a sign of poor-quality sleep, which could mean missing out on some of sleep's restorative benefits
• Occur along with a sedentary lifestyle and poor dietary choices, both of which research has shown are more common in over-sleepers
• Reflect a mismatch between internal and external timing cues—a type of mismatch linked to health conditions such as diabetes

Keep in mind: Sleeping a lot may be not only a cause but also a consequence of health issues. And in some cases, it may be an early warning sign that tips you off to a health risk, so you can take preventive action before a more serious problem develops.

Going to the other extreme: Too Little Sleep

At the other end of the sleep-duration continuum, sleeping too little has also been linked to a wide range of health conditions. According to the  American Academy of Sleep Medicine, regularly sleeping less than seven hours per night increases the risk for:

Obesity

• Diabetes
• High blood pressure
• Heart disease
• Stroke
• Mental health issues
• Premature death

In the metabolic syndrome study, both men and women who slept fewer than six hours were more likely to have a large waistline than those who slept a normal amount. Men who skimped on sleep were also more likely to have metabolic syndrome.

You and your sleep

How do under-sleeping and over-sleeping compare? To answer that question, researchers have looked at how sleep duration is related to  type 2 diabetes,  cardiovascular disease, and death from all causes. Many studies have found a U-shaped relationship. In other words, the risk seems to be highest at the extremes of either very short or very long sleep and lowest in the middle, at about seven to eight hours of sleep per night.

Bottom line: Sleeping either too much or not enough on a regular basis is associated with health problems. If you're concerned that you may not be getting a healthy amount of sleep, talk with your health care provider.